*{
    margin: 0 auto;
    padding: 0;
    box-sizing: border-box;
}
body{
    max-width: 540px;
    min-width: 320px;
    margin: 0 auto;
    color: #000;
    background-color: #f2f2f2;
    /* 禁止出现水平滚动条 */
    overflow-x: hidden;
}
li {
    list-style: none;
}
a {
    text-decoration: none;
    color: #666;
}
img {
    vertical-align: middle;
}
input {
    outline: none;
}
/* 清除浮动 */
.clearfix::after {
    content: "";
    display: block;
    height: 0;
    visibility: hidden;
    clear: both;
}